Surface to Groundwater Interactions beneath the City of Berlin: Results from 3D Models

Abstract

Knowing the thermal and hydraulic conditions below major urban centers is of increasing importance in the context of energy and water supply. With this study, focusing on the major urban center of Berlin, Germany, we aim to gain insights on the coupling of surface water bodies to the subsurface thermal and hydraulic field investigating shallow water to deep groundwater interactions. Therefore, we use a 3D structural model of the subsurface, constrained by all available data and observations, as a base for simulations of the coupled transport of fluid and heat. This model resolves the 3D configuration of the main geological units and thus enables us to account for related heterogeneities in physical properties. Additionally, we resolve surface water body geometries with newly available data. To assess how surface water bodies interact with the deeper groundwater at different depths in the model domain, the influence of different hydraulic boundary conditions is quantified, which indicates that the coupling of surface water bodies and groundwater strongly modifies predicted groundwater circulation. Consequently, changes in subsurface temperatures are also predicted, where lakes may account for temperature differences up to ±5°C and rivers could account for up to ±1°C visible at depths ≤-500 m.a.s.l. These differences are mainly connected to changes in the advective component of heat transport caused by the modifications of the hydraulic boundary condition. Pressure-driven heat transport is most efficient where differences between hydraulic heads of aquifers and surface water bodies are highest. This study therefore illustrates the impact of surface to subsurface water interactions in an urban context.

Boundary condition control on inter-aquifer flow in the subsurface of Berlin (Germany) – new insights from 3-D numerical modelling

“…Neogene Colmation Layer 1.64 1.3 × 10 −6 1.81 0.237 4.8 × 10 −8 Holocene to Weichselian 2.71 0.9 × 10 −6 1.57 0.320 2.1 × 10 −4 Eemian to Saalian 2.59 0.9 × 10 −6 1.58 0.314 1.5 × 10 −5 Holstein 2.17 0.9 × 10 −6 1.67 0.296 3.4 × 10 −7 Elsterian 2.35 0.9 × 10 −6 1.61 0.304 1.3 × 10 −5 Miocene 2.47 1.0 × 10 −6 1.56 0.301 9.0 × 10 −6 to Sippel et al 2013and Frick et al (2019) for details on the parametrisation adopted for the deeper model units. Hydraulic conductivity values have been determined following the approach of Devlin (2017), the latter being based on a geometric mean average weighted by the grain size distribution of the respective mineral assemblage.…”

“…The 3-D structural model used in this study has been previously described in Frick et al (2019) and differentiates 21 geological units, 9 Cenozoic, 8 Mesozoic and 2 Paleozoic, for the sedimentary succession and 2 units for the underlying basement. The sedimentary succession can be subdivided into four major compartments, namely the shallow, intermediate, deep and very deep aquifer systems (Fig.…”

“…The very deep compartment is separated from above by a thick layer of Permian Zechstein salt, which shows a highly heterogeneous thickness distribution (Fig. 1a, Frick et al, 2019) with some local discontinuities possibly leading to deep inter-aquifer flow. This compartment also shows a very high salinity of the fluids mainly related to seawater evaporation during depositional times (Lüders et al, 2010).…”

“…For the problem at hand, we carried out 3-D coupled fluid and heat transport simulations based on the commercial software FEFLOW©. Our hydrogeological model (Haacke, 2018) resolves all relevant geological interfaces (21 geological layers) and the surface hydrology, meaning major lakes and rivers and was created with the commercial software Petrel (© Schlumberger).…”

3-D Simulations of Groundwater Utilization in an Urban Catchment of Berlin, Germany

“…The database is partly confidential and can therefore not be shared at this point in time. For further information on the model setup and database please refer to Frick et al (2016Frick et al ( , 2018b.…”